SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'en' 
WHERE 
  pfv.variant_id IN (
    1712, 1748, 2347, 2345, 2344, 1659, 1975, 
    2325, 2343, 1973, 2137, 1705, 2138, 
    2000, 1983, 1937, 1995, 1902, 1900, 
    1787, 2341, 2351, 1789, 1905, 1946, 
    2075, 1694, 1941, 1942
  )

Query time 0.00054

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "30.46"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 29,
          "rows_produced_per_join": 29,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`pfv`.`variant_id` in (1712,1748,2347,2345,2344,1659,1975,2325,2343,1973,2137,1705,2138,2000,1983,1937,1995,1902,1900,1787,2341,2351,1789,1905,1946,2075,1694,1941,1942))",
          "cost_info": {
            "read_cost": "17.41",
            "eval_cost": "2.90",
            "prefix_cost": "20.31",
            "data_read_per_join": "33K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ]
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "gaseus.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 29,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "7.25",
            "eval_cost": "2.90",
            "prefix_cost": "30.46",
            "data_read_per_join": "90K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}